shouting versus dotting

[Sergey Gromov]

Sat, 04 Oct 2008 23:50:47 -0500,
Andrei Alexandrescu wrote:
> Alexander Panek wrote:
> > Andrei Alexandrescu wrote:
> >> The problem I see with "!" as a template instantiation is not 
> >> technical. I write a fair amount of templated code and over years the 
> >> "!" did not grow on me at all. I was time and again consoled by Walter 
> >> than one day that will happen, but it never did. I also realized that 
> >> Walter didn't see a problem with it because he writes only little 
> >> template code.
> >>
> >> I didn't have much beef with other oddities unique to D. For example, 
> >> I found no problem accommodating binary "~" and I was wondering what 
> >> makes "!" different. I was just looking at a page full of templates 
> >> and it looked like crap.
> >>
> >> One morning I woke up with the sudden realization of what the problem 
> >> was: the shouting.
> >>
> >> In C, "!" is used as a unary operator. That may seem odd at first, but 
> >> it nevers follows a word so it's tenuous to associate it with the 
> >> natural language "!". In D, binary "!" _always_ follows a word, a 
> >> name, something coming from natural language. So the conotation with 
> >> exclamation jumps at you.
> >>
> >> That's why I find the choice of "!" poor. I believe it can impede to 
> >> some extent acquisition of templates by newcomers, and conversely I 
> >> believe that using .() can make templates more palatable. I tried 
> >> using ".()" in my code and in only a couple of days it looked and felt 
> >> way better to me. Based on that experience, I suggest that "!()" is 
> >> dropped in favor of ".()" for template instantiation for D2.
> >>
> >> Sean's argument that "The exclamation mark signifies an assertion of 
> >> sorts" is exactly where I'd want templates not to be: they should be 
> >> blended in, not a hiccup from normal code. Serious effort has been, 
> >> and still is, made in D to avoid shell-shocking people about use of 
> >> templates, and I think ".()" would be a good step in that direction.
> > 
> > Sean has a point. Templates are not runtime constructs. So a clear 
> > distinction between instantiating a function with a given type and just 
> > calling a function that has fixed argument types and a fixed return type 
> >  is necessary.
> 
> Why? This sounds objective, so you better back it up. Au contraire, I 
> see absolutely, but absolutely no need for a distinction. If it weren't 
> for syntactic difficulties, to me using straight parentheses for 
> template instantiation would have been the perfect choice. (How many 
> times did you just forget the "!"? I know I often do. Why? Because most 
> of the time it's not even needed.)
> 
> > The exclamation mark gives us this clear distinction and 
> > has served well in terms of readability for me, especially because it 
> > jumps out ? not because it?s an exclamation mark, thus having a meaning 
> > in natural language, but rather just because of its form. A straight 
> > vertical line with a dot underneath it. That just works perfectly well 
> > as seperator between identifier/type and type argument.
> 
> I believe the clear distinction is not only unnecessary, but 
> undesirable. We should actively fight against it.

You have a problem with shouting.  Not everyone has.

The distinction is important IMHO because the choice between template 
and runtime is a speed/size tradeoff choice.  It's better to make it 
explicitly.